@InProceedings{BatistaShimLawrAntu:1993:ElNiEf,
               author = "Batista, Getulio Teixeira and Shimabukuro, Yosio Edemir and 
                         Lawrence, William T. and Antunes, Mauro A. H.",
                title = "El Nino effect on Amazon vegetation cover through NOAA-AVHRR",
            booktitle = "Resumos...",
                 year = "1993",
                pages = "37",
         organization = "Simp{\'o}sio Latino-Americano em Percepcion Remota, 6.",
             keywords = "AGRONOMIA, AMAZONIA LEGAL, INDICE DE VEGETACAO, EL NINO, COBERTURA 
                         VEGETAL, NOAA, AVHRR, NDVI.",
             abstract = "This paper shows results of an experiment that explored a 
                         long-term temporal variation of the vegetation index NDVI 
                         (Normalized DifferenceVegetation Index)of several vegetation 
                         covers that occur in the Brazilian LegalAmazon. The value of NDVI 
                         obtained from NOAA satellites, has veem shown for the estimation 
                         of a number of ecosystem variables, such as leaf area index and 
                         photosynthetic active absorbed radiation by the canopy, which in 
                         turn are essential for modeling of gases, mass, and energy 
                         exchange between the biosphere and the atmosphere, contributing 
                         therefore, for the understanding fo global change processes. The 
                         phenology of natural vegetation under diversi climatic conditions 
                         due not only to seasonal variation but also episodic events sych 
                         ENSO (El Nino Southern Oscillation)is important for the 
                         understanting of these processes. Long-term monitoring (August 
                         1981 to June 1991)of 8 vegetation types (Dense Forest 
                         {"}Submontana{"} and {"}Terras Baixas{"}), open Forest 
                         ({"}Submontana{"}and {"}Terras Baixas{"}), transition Forest, 
                         Seasonal Forest ({"}Caatinga{"}), and tow types of {"}Cerrado{"} 
                         which occur in the northern part of Brazil (3 N-19S and 35W and 
                         74W)is discussed. For each vegetation type, 10 samples of 3x3 
                         pixels were selected and monthly composites of NDVI were obtained 
                         from GAC ({"}Global Area Coverage{"})data. Yearly composites of 
                         NDVI were obtained ro verify the inter-annual climatic variation 
                         due to ElNino occurence. Throughout the analysis of 10 years of 
                         data is was clearly noteced the variation on the NDVI due to 
                         differene satellites, indicating the need for calibration of AVHRR 
                         data for multitemporal studies. Therefore, a calibration procedure 
                         proposed by NASA Goddard Space Flight Center and the University of 
                         Maryland (Los, 1993)were applied to the data to make possible 
                         quantitative comparisons of NDVI values obtained at different 
                         times. Seasonality of {"}Cerrado{"} and especially of 
                         {"}Caatinga{"} , is outstanding NDVI values vary from 3 to 4 times 
                         for the {"}Cerrado{"} and {"}Caatinga{"} respectively, in extreme 
                         years. Preserved {"}Cerrado{"}({"}parque{"})was always distinct 
                         from Dense Forest ({"}Terra Firme{"})in any season ofany year 
                         analyzed, however, better distinction is found during the dry 
                         season, especially in September. A comparison between normal an El 
                         Nino years indicated the influence of this phenomenon on the 
                         phenology of the forest vegetation. The phenology of forest cover, 
                         except {"}Caatinga{"} and {"}Cerrado{"} does not vary much 
                         throughout the year, however, for El Nino years, as 1983, there is 
                         a clear reduction in the NDVI values during the dry season, 
                         especially for the Transition ForestThis indicates the importance 
                         of multitemporal data for the characterization of forest 
                         ecosystems. Dense vegetation covers showed high NDVI values 
                         (-0,5), {"}Caatinga{"}had an average NDVI value -0,3 with large 
                         seasonal variation, and {"}Cerrado{"}had average NDVI value -0,3 
                         with great seasonal variation but never reaching the{"}Caatinga{"} 
                         greeness peak (NDVI-0,5).",
  conference-location = "Cartagena, CO",
      conference-year = "03-08 oct. 1993",
                label = "6767",
         organisation = "SELPER",
           targetfile = "Batista_el nino.pdf",
        urlaccessdate = "02 maio 2024"
}